The present invention is directed to an electrodynamic acoustic transducer comprising a magnet system and a vibration system formed by a diaphragm and a wire coil supported by the diaphragm. The diaphragm has two differently profiled parts performing distinct operations.
The diaphragm has an acoustically active central part with a domed top, commonly referred to as a cap. This central part is surrounded by a coil seat, the electric coil of the transducer being attached to the latter. An annular part which provides for the resilient suspension of the diaphragm and has, e.g., a curved profile, proceeds from the shoulder. This annular part is commonly referred to as a bead. Seemingly contradictory requirements must be satisfied in order to achieve optimal operation of the central part and annular part.
In order to achieve a high degree of sensitivity in the electrodynamic acoustic transducer, the diameter of the acoustically active central part should be as large as possible. Further, it is desirable to make the central part as rigid as possible for a good acoustic effect. Only in this way can an effective interaction be ensured between the central part and the air which acts as an acoustical medium, regardless of whether the transducer is used as an acoustic receiver or as an acoustic transmitter. The rigidity of the annular part must be as slight as possible in order to ensure a good axial movability of the central part. For this purpose, the annular part must also be constructed with a relatively large annular width. In known acoustic transducers, the annular part is arranged radially outside the central part and hence adds to the diameter of the central part. As a result, diaphragms in the known transducers had large dimensions which could not be reconciled with the given limited dimensions of a transducer casing so that it was necessary to reach a technical compromise: either the dimensions of the central part and accordingly the dimensions of the coil had to be reduced or the annular part had to be constructed with a smaller annular width.